This section is intended to introduce the reader to various aspects of art that may be related to aspects of the present technique, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present technique. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Over the past decade, the demand for flat panel displays has increased significantly. Flat panel displays have been incorporated into computer monitors, televisions, cellular phones, personal digital assistants (PDA's), instrumentation, monitoring devices, and the like. Flat panel displays include liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, and liquid plasma displays. However, existing flat panel displays generally have one or more undesirable characteristics, such as unsatisfactory image quality, high power consumption, low light output, display size constraints, and incompatibility with certain environmental conditions.
Existing flat panel displays generally include brightness enhancing films, antireflective layers, polarizers, color filters, absorptive layers, and many other layers. These layers undesirably add to the cost, complexity, and thickness of the flat panel displays, while often drastically reducing the light output of the display. As a result, existing flat panel displays are not particularly energy efficient.
Flat panel displays also commonly employ a spatial additive color technique, which adversely limits the resolution of the display. In general, the resolution of flat panel displays is characterized by the horizontal and vertical number of pixels. In the spatial additive color technique, each pixel includes a group of differently colored cells (e.g., red, green, and blue) arranged in close proximity to one another. Due to the close proximity, the group of differently colored cells is perceived by the eye as a single color. The use of multiple cells per pixel undesirably increases the cost and complexity of the flat panel display, while also limiting the resolution of the display.
The distribution of light from the light source affects the image quality expelled from the flat panel display. Flat panel displays, particularly LCD displays, typically have either an edge light or a backlight as the light source. One challenge of edge injection of light is the variation in the light intensity across the waveguide from one edge to another of the display. The nonuniformity in light intensity emitted or transmitted from pixels (i.e., luminosity) across the surface of the waveguide generally worsens with increasing display or screen size. In addition, luminosity across the waveguide is further degraded as a result of open pixels located closer to the edge light source which emit light and, consequently, deplete the light within the waveguide available to open pixels further away from the edge light source. To circumvent such challenges, large LCD displays generally inject light from behind the display rather than from the edge, however among other drawbacks, the backlight undesirably adds to the overall thickness of the display. In plasma displays, the light originates from many tiny cells of an inert mixture of noble gases (e.g., neon and xenon) between two panels of glass. The cells emit light upon electrically turning the gas into plasma which, in turn, acts upon phosphors to emit photons. Current challenges of plasma displays are that they are particularly heavy, energy inefficient, and subject to decreasing luminosity with use.
Flat panel displays that employ a transparent slab waveguide for directing light to a plurality of pixel shuttering mechanisms can provide quality images while exhibiting high efficiency, low power consumption, and a thin form factor. In these waveguide systems, light is injected from an edge of the waveguide (edge-injected) to provide a light-recycling backlight and/or to supply light that is directed to pixels located near the display surface of the waveguide. For example, edge-injected light may be directed to the display surface by the pixel shuttering mechanisms. Thus, light generated in a light source is distributed into the waveguide, and then expelled from the waveguide at a pixel location on a surface of the waveguide. To provide a uniform image it is desirable that light injected into the waveguide remain uniform across the waveguide such that the light intensity of the light expelled at each active or open pixel (i.e., “on” pixel) location is uniform. This may be referred to as having a high luminous uniformity. In some implementations edge-injected light may not be uniformly distributed within the waveguide and/or light depletion due to open pixels may cause light nonuniformity within the waveguide, resulting in a low luminous uniformity and, thereby, images that do not exhibit uniform intensity, color, brightness, and the like. Furthermore, achieving high luminous uniformity becomes increasingly more difficult as the thickness of the flat panel display, and, thus, the thickness of the waveguide decreases. It would be an improvement in the art to provide a light injection system and method that enhances luminous uniformity throughout a waveguide regardless of panel size (length×width) and thickness. The trend towards thinner panels can then be accommodated without undue degradation of luminous uniformity of the images displayed thereon.